Vehicle notification sound emitting apparatus

ABSTRACT

A vehicle notification sound emitting apparatus is basically provided with a sound emitting device and a notification sound control device. The sound emitting device is configured to emit a movement notification sound to an outside of a vehicle to inform a person in an area surrounding the vehicle that the vehicle will move. The notification sound control device is configured to operate the sound emitting device in response to occurrence of a vehicle condition. The notification sound control device setting the movement notification sound of the sound emitting device to a frequency in a range of 1.5 kHz to 6 kHz.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to Japanese Patent Application Nos. 2010-026117, 2010-026118 and 2010-026123, filed Feb. 9, 2010. The entire disclosures of Japanese Patent Application Nos. 2010-026117, 2010-026118 and 2010-026123 are hereby incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention generally relates to vehicle sound emitting technology for informing a person in an area surrounding of the vehicle that the vehicle is moving, or is about to move, in an advancement direction, e.g., forward or rearward. More specifically, the present invention relates to a vehicle notification sound emitting apparatus that emits a notification sound to inform people of the existence of the vehicle.

2. Background Information

Some vehicles have a very quiet operating sound and/or moving sound (including a vehicle equipped with an internal combustion engine). For example, an electric powered vehicle such as an electric car configured to be electrically driven (EV drive) using only an electric motor is typically very quiet while operating and/or moving. Also for example, a hybrid vehicle having an electric drive mode (EV mode) in which the vehicle is driven solely with an electric motor is typically very quiet while operating and/or moving. In such very quiet vehicles, the operating sound and/or moving sound (vehicle information) such as the existence of the vehicle, an intent of a driver as indicated by a gear shift or other operation, an advancement direction of the vehicle (forward or reverse), a vehicle speed and/or other traveling condition of the vehicle are often not perceivable to a person in a surrounding area of the vehicle by emitting a notification sound to the outside of the vehicle. Thus, while typically it is desirable for the occupants of the vehicle to have a very vehicle, there are times when it is desirable for the vehicle convey the existence of the vehicle to a person in a surrounding area of the vehicle by emitting a notification sound to the outside of the vehicle.

Among the vehicle information mentioned above, technology has been proposed for emitting a movement notification sound to inform a person in an outside area surrounding a vehicle that the vehicle is moving in a forward direction or a reverse direction, (i.e., an advancement direction). For example, conventional movement notification sound technology is disclosed in Japanese Laid-Open Patent Publication No. 2002-233001 in which a movement notification sound is emitted to indicate movement of the vehicle in an advancement direction. More specifically, this patent publication presents a technology in which a pseudo engine sound resembling the sound of a vehicle driven by an engine is emitted as a movement notification sound. Another example conventional movement notification sound technology is disclosed in Japanese Laid-Open Patent Publication No. 2004-136831 in which a notification sound emitting apparatus emits a forward movement notification sound for informing a person in a surrounding area of a vehicle that the vehicle is moving forward when the vehicle has started moving forward from a stop. Still another example conventional movement notification sound technology is disclosed in Japanese Laid-Open Patent Publication No. 2005-343360 in which a notification sound emitting apparatus emits a forward movement notification sound for informing a person in a surrounding area of a vehicle that the vehicle is moving forward when the vehicle has started moving forward from a stop. A volume of the notification sound is changed between when the vehicle is starting into motion and when the vehicle is moving. With theses conventional vehicle notification sound emitting apparatuses, a person in an area surrounding the vehicle can recognize that a moving vehicle is nearby by hearing the pseudo engine sound or other sound and exercise caution. Thus, the apparatus aids in preventing accidents.

SUMMARY

It has been discovered that the conventional vehicle notification sound emitting apparatus, such as the ones mentioned above, merely emits a pseudo engine sound as a movement notification sound. However, this conventional technology does not control the quality of the notification sound. Thus, there is no assurance that a movement notification sound emitted from a conventional vehicle notification sound emitting apparatus will be easily heard by a person in an area surrounding the outside of the vehicle. Depending on the environment, the notification sound may be difficult to hear and a sufficient notification effect may not be achievable in a conventional vehicle notification sound emitting apparatus.

As explained in Japanese Laid-Open Patent Publication No. 2002-233001, it is necessary to adopt a special measure, such as increasing the volume of the moving notification sound, when the vehicle is in an environment where it is difficult for the notification sound to be heard. However, the cost of the apparatus and increases the rate of failures of the notification sound emitting apparatus increases when a detection device is provided for checking the surrounding environment and a volume increasing device is provided for increasing the volume of the sound.

Even if the moving notification sound is configured to have a tone that is more easily heard by a person in an area surrounding the vehicle such that the special measures mentioned above are not necessary, there will be other problems that will now be explained. The moving notification sound is a notification intended for people outside the vehicle. The moving notification sound is not necessary for a driver or passenger inside the vehicle. If the moving notification sound emitted outside the vehicle penetrates a cabin interior (passenger compartment) of the vehicle, then the moving notification sound may be unpleasant for a driver and/or passengers inside the vehicle. This is particularly the case when the moving notification sound is a pseudo engine sound like that described in Japanese Laid-Open Patent Publication No. 2002-233001. Also the moving notification sound may be unpleasant for a driver and/or passengers inside the vehicle if the moving notification sound is configured to be emitted continuously for long periods of time in comparison to other vehicle information notifications.

One aspect of the present disclosure is to provide a vehicle notification sound emitting apparatus that can emit a moving notification sound (e.g., either a forward movement notification sound or a reverse movement notification sound) that can be heard easily by a person in an outside area surrounding the vehicle, but which does not easily penetrate a cabin interior of the vehicle from outside the vehicle. Thus, with this type of vehicle notification sound emitting apparatus, a person in an outside area surrounding the vehicle can hear the movement notification sound in a reliable fashion without using a sound volume increasing device or other special measure, and avoid a situation in which an unnecessary movement notification sound penetrates into the cabin interior that becomes unpleasant for a driver and/or passenger.

Another aspect of the present disclosure is to provide a vehicle notification sound emitting apparatus that can convey speed information and distance information regarding a vehicle to a person in a surrounding area of the vehicle.

Still another aspect of the present disclosure is to provide a vehicle notification sound emitting apparatus that can emit notification sounds indicating that a vehicle is in a state of starting into motion or a state of motion (moving) without disturbing a driver.

In view of the above mentioned conventional technology, a vehicle notification sound emitting apparatus according to the present disclosure as will now be explained. The basic features of a notification sound emitting apparatus according to the present disclosure are based on the premise that the apparatus will serve to emit a movement notification sound to inform a person in a surrounding area that the vehicle is moving.

A vehicle notification sound emitting apparatus according to the present disclosure is proposed that basically comprises a sound emitting device and a notification sound control device. The sound emitting device is configured to emit a movement notification sound to an outside of a vehicle to inform a person in an area surrounding the vehicle that the vehicle will move. The notification sound control device is configured to operate the sound emitting device in response to occurrence of a vehicle condition. The notification sound control device setting the movement notification sound of the sound emitting device to a frequency in a range of 1.5 kHz to 6 kHz.

These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the notification sound emitting apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of this original disclosure:

FIG. 1 is a control block diagram showing a control system or vehicle notification sound emitting apparatus including a notification sound controller for controlling a notification sound emitting device of the vehicle notification sound emitting apparatus in accordance with an illustrated embodiment;

FIG. 2 is a flowchart showing a control program executed by the notification sound controller shown in FIG. 1 in order to control starting a starting forward movement notification sound S;

FIG. 3 is a flowchart showing a control program executed by the notification sound controller shown in FIG. 1 in order to control a forward moving notification sound D;

FIG. 4 is a flowchart showing a control program executed by the notification sound controller shown in FIG. 1 in order to control a reverse movement notification sound R;

FIG. 5 is a flowchart showing a control program executed by the notification sound controller shown in FIG. 1 in order to prohibit emitting a notification sound from the notification sound emitting device;

FIG. 6 is a flowchart showing a control program executed by the notification sound controller shown in FIG. 1 in order to increase a volume of a notification sound emitted from the notification sound emitting device;

FIG. 7 is a characteristic diagram showing examples of a cabin interior sound insulating property for two vehicles A and B;

FIG. 8 is a characteristic diagram showing equal loudness level curves expressing a sensitivity of a human ear; and

FIG. 9 is a map expressing a frequency setting control executed by the notification sound controller to control a frequency of the forward moving notification sound D.

DETAILED DESCRIPTION OF EMBODIMENTS

Selected embodiments will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

Referring initially to FIG. 1, a vehicle notification sound emitting apparatus is illustrated in accordance with one embodiment. More specifically, FIG. 1 is a control system diagram showing a control system for controlling notification sound emitting devices of the vehicle notification sound emitting apparatus. In this illustrated embodiment, a cabin exterior speaker 1 is provided as an exterior notification sound emitting device for issuing a notification to a person (e.g., pedestrian or motorcycle rider) in an outside area surrounding the vehicle. Also in this illustrated embodiment, a cabin interior speaker 11 is provided as an interior notification sound emitting device for issuing a notification to a driver.

In the illustrated embodiment, a vehicle in which the notification sound emitting apparatus is used is an electric car that has only an electric motor as a power source and is driven electrically (EV drive) using the electric motor. However, it should be clear from this disclosure that the vehicle notification sound emitting apparatus disclosed herein can also be applied to a hybrid vehicle having both an electric motor and an engine as power sources, where the vehicle is driven solely with the electric motor in an electric drive mode (EV mode), and driven with power from both the electric motor and the engine in a hybrid mode (HEV mode). Likewise, the vehicle notification sound emitting apparatus disclosed herein can be applied to an engine driven vehicle having only an engine as a power source.

In the illustrated embodiment, the cabin exterior speaker 1 is arranged in a space inside a motor room of a frontward portion of the vehicle. The motor room of the vehicle is where a power unit is located that includes an electric motor serving as a power source of the electric car and a transmission. More specifically, the cabin exterior speaker 1 is arranged in a space where mud, rocks, and other contaminants picked up by the wheels will not enter the speaker and such contaminants as rain, snow, and water from a high-pressure car wash will not enter the speaker. By using this space as a resonance box for the cabin exterior speaker 1, the notification sound emitting apparatus according to this embodiment can be made into a non-directional sound source.

The cabin exterior speaker 1 and the cabin interior speaker 11 are controlled by a notification sound controller as shown in FIG. 1. The notification sound controller 12 receives signals from a range sensor 13, a vehicle speed sensor 14, a brake switch 15, a mute switch 16, a sound volume increasing switch 17, an ignition switch 18 and an obstacle distance sensor 19. In this illustrated embodiment, the notification sound controller 12 corresponds to a notification sound control device or section. Basically, the notification sound controller 12 is configured to operate the speakers 1 and 11 (e.g., the sound emitting devices) in response to occurrence of a vehicle condition such as vehicle movement or preparation to vehicle movement. The speakers 1 and 11 emit various movement notification sounds depending on the vehicle condition. The term “movement notification sound” is generically used herein to refer to both actual vehicle movement as well as preparation for starting vehicle movement in a forward advancement direction and/or a reverse advancement direction. The term “drivable state” as used here in refers to a vehicle in a nonmoving state but with the vehicle ready to move upon operating an accelerator or the like.

The range sensor 13 is configured to detect if the vehicle transmission is set to Park (P), Reverse (R), Neutral (N), or Drive (D) by reacting to a shift (range selection) operation performed by a driver to park the vehicle or designate a desired movement direction.

The vehicle speed sensor 14 is configured to detect a vehicle speed V. The brake switch 15 is configured to turn ON when the vehicle is being braked by depressing a brake pedal and OFF when the vehicle is not being braked (brake pedal is released). The mute switch 16 is configured to be manually pressed in order to mute a sound emitted from the cabin exterior speaker 1. The sound volume increasing switch 17 is configured to be pressed in order to increase the volume of a sound emitted from the cabin exterior speaker 1. The ignition switch 18 is configured to put the power unit into a drivable state and outputs an ON/OFF signal to the notification sound controller 12 depending on the position of the ignition switch 18. The obstacle distance sensor 19 is configured to detect a distance L between the host vehicle and another vehicle or other obstacle in front of the vehicle.

Now, the manner in which the notification sound controller 12 operates the cabin interior speaker 11 in this embodiment will now be explained. In the case where the transmission is shifted to reverse (R), an R range selection signal will be received by the notification sound controller 12 from the range sensor 13. In response to receiving the R range selection signal, the notification sound controller 12 drives the cabin interior speaker 11 to emit an “R range selection notification sound.” The R range selection notification sound informs the driver that the R range has been selected. In the illustrated embodiment, the R range selection notification sound is an intermittent sound. In the case where an obstacle's distance L from the host vehicle is smaller than a preset distance, an obstacle detection signal will be received by the notification sound controller 12 from the obstacle distance sensor 19. In response to receiving the obstacle detection signal, the notification sound controller 12 drives the cabin interior speaker 11 to emit an “obstacle proximity notification sound” using, for example, a voice to inform the driver that the vehicle is close to an obstacle.

There are other notification sounds emitted inside the vehicle cabin to warn a driver, such as a “seatbelt notification sound” (not shown in the figures) emitted to warn that a seatbelt is not latched. However, the seatbelt notification sound is not emitted from the cabin interior speaker 11, but from a separate dedicated speaker or buzzer that is different from the cabin interior speaker 11 that is used by the notification sound controller 12 for notification that the vehicle is close to an obstacle. In other words, in the illustrated embodiment, the cabin interior speaker 11 is a separate and distinct notification sound emitting device from those used for other notification sounds emitted inside the vehicle cabin.

Operational control of the cabin exterior speaker 1 executed by the notification sound controller 12 shown in FIG. 1 will now be explained. In this embodiment, the movement notification sounds emitted from the cabin exterior speaker 1 include, but not limited to, a starting forward movement notification sound S, a forward moving notification sound D and a reverse movement notification sound R. The starting forward movement notification sound S (also called “S” sound) is emitted as a notification before the vehicle starts moving forward. The forward moving notification sound D (also called “D” sound) serves as a movement notification sound that is emitted when the vehicle is actually moving forward. The reverse movement notification sound R (also called “R” sound) serving as a movement notification sound emitted when the vehicle is actually moving in reverse and/or has been shifted in a reverse gear. The starting forward movement notification sound (S sound) and the forward moving notification sound (D sound) together constitute a forward advancement notification sound serving to notify about forward movement of the vehicle when the vehicle is in the D range.

The starting forward movement notification sound S is a soft sound similar to an electronic ring tone produced by a software phone, the forward moving notification sound D is a pseudo engine sound resembling an engine sound generated when an engine-driven vehicle moves, and the reverse movement notification sound R is the same intermittent sound as the R range selection notification sound emitted from the cabin interior speaker 11 when the R range is selected.

As just mentioned, the forward moving notification sound D is a pseudo engine sound and it is emitted for a long period of time. Consequently, it could be annoying to listen to the forward moving notification sound D continuously, and it is not necessary for a driver to hear the forward moving notification sound D. Conversely, the starting forward movement notification sound S is a soft sound like that of a software phone and it is only emitted for a short period of time from immediately before the vehicle starts moving forward until the vehicle starts moving forward. Thus, the starting forward movement notification sound S is not annoying to a driver and is preferably heard by the driver so that the driver can know that a starting forward notification has been emitted.

In view of these requirements, in this embodiment, the forward moving notification sound D is configured to be a pseudo engine sound as will now be explained and the starting forward movement notification sound S is set to a soft sound like that emitted by a software phone as will be explained later.

In order to consider a sound insulating property of a cabin of the vehicle, FIG. 7 shows an example of a cabin interior sound insulating property of two basic vehicles A and B (with windows closed) expressed as a plot of an acoustic transfer characteristic (dB) versus a ⅓ octave center frequency (Hz). Basically, the vehicles A and B have metal and/or plastic body panels with glass windows, which are typical of most vehicles. Although the two vehicles are slightly different, both vehicles, typical of most vehicles, clearly exhibit a similar trend of the sound insulating property increasing with increasing frequency. At frequencies of 1.5 kHz and higher, the volume of a D sound penetrating into the vehicle cabin from the outside can be suppressed to a permissible level.

Since the forward moving notification sound D is intended to notify a person in an outside area surrounding the vehicle that the vehicle is moving forward, it is also necessary for the forward moving notification sound D to be readily audible and clearly heard by a person hearing the forward moving notification sound D directly in the area surrounding the vehicle.

Therefore, in order to consider a sensitivity of a human ear, FIG. 8 shows equal loudness level curves typically used to discuss ear sensitivity. Each curve is a frequency characteristic comprising a plot of sound pressure level (equal loudness level) versus frequency (Hz) corresponding to a given perceived volume (loudness: phon). That is, for each of several sound volumes (20 phon, 40, phon, 60 phon, 80 phon and 100 phon in FIG. 8), sound pressure levels (equal loudness levels) dB that are perceived to have, i.e., sound like they have, the same volume are plotted to obtain a curve. As a sound pressure level (equal loudness level) dB becomes lower, the sound pressure level at which the same perceived volume (20 phon, 40 phon, 60 phon, 80 phon, or 100 phon) can be heard becomes smaller, i.e., the easier it is for a person to hear the sound.

Sounds that have a low sound pressure level (equal loudness level) dB and can be easily heard by a human ear lie in a range of frequencies from 1.5 kHz to 6 kHz indicated as an adequately audible region in FIG. 8. In other words, the adequately audible region corresponds to a frequency range in a vicinity where the equal loudness level curves corresponds to a minimum sound pressure level. This frequency range of 1.5 kHz to 6 kHz overlaps with the frequency range of 1.5 kHz and higher mentioned previously regarding FIG. 7 as a frequency range in which a volume of a D sound penetrating into the vehicle cabin from outside the vehicle can be suppressed to a permissible level.

Therefore, in this embodiment, the forward moving notification sound D is a pseudo engine sound in a frequency range (1.5 kHz to 6 kHz) that can be readily heard by a person in an outside area surrounding the vehicle. As a reference, the frequency range of an actual engine sound is 200 to 400 Hz, which is considerably lower than the selected frequency range (1.5 kHz to 6 kHz) for the forward moving notification sound D. In this way, vehicle occupants (e.g., the driver and passengers) are prevented from hearing the forward moving notification sound D unnecessarily inside the vehicle cabin. In this way, vehicle occupants (e.g., the driver and passengers) are prevented from being annoyed by the forward moving notification sound D (pseudo engine sound). Meanwhile, a person in an area surrounding the vehicle can readily hear the forward moving notification sound D (pseudo engine sound) and be ensured to recognize that the vehicle exists and is moving.

Additionally, there are operational effects that can be obtained if an upper limit frequency of the forward moving notification sound D is set to 6 kHz as explained above. These operational effects will now be explained. As a person ages, it becomes more difficult to detect sounds having higher frequencies. In particular, a difficulty of hearing sounds having frequencies higher than 6 kHz increases quadratically with increasing age. Therefore, by setting an upper limit frequency of the forward moving notification sound D to 6 kHz, the ability of an older person in an area surrounding the vehicle to hear the forward moving notification sound D can be ensured, which is advantageous from a safety standpoint.

The frequency range mentioned above (1.5 kHz to 6 kHz) is a permissible frequency range for the forward moving notification sound D, but not an optimum frequency range. Although sounds in the frequency range of 1.5 kHz to 6 kHz do not readily enter the vehicle cabin from outside the vehicle, an optimum frequency range for making the forward moving notification sound D readily audible to a person in an area surrounding the vehicle is the frequency range 2 kHz to 4 kHz as indicated in FIG. 8. The frequency range 2 kHz to 4 kHz is a more preferable audible frequency range considering a sensitivity of the human ear is highest in this frequency range due to resonance of the external ear canal. Thus, it should be clear that it is preferable for the frequency of the forward moving notification sound D to be in this optimum frequency range of 2 kHz to 4 kHz.

In view of the propagation properties of sound between the inside and outside of the vehicle cabin, a vehicle is typically constructed such that sounds with comparatively high frequencies (typically 1.5 kHz to 6 kHz, although it varies depending on the vehicle) do not easily penetrate the cabin interior from outside the cabin. However, a vehicle is typically constructed such that sounds with comparatively low frequencies (typically below 1.5 kHz, although it varies depending on the vehicle) do easily penetrate the cabin interior from outside the cabin. Therefore, in this embodiment, the forward moving notification sound D is configured to be a pseudo engine sound in a prescribed range of comparatively high frequencies (preferably 2 kHz to 4 kHz) that do not easily enter the cabin interior from outside the cabin. In this way, the forward moving notification sound D is not heard unnecessarily by a driver inside the vehicle cabin. As a result, the forward moving notification sound D (pseudo engine sound) does not become an annoyance to the driver. Moreover, forward moving notification sound D (pseudo engine sound) is readily heard by a person in an outside area surrounding the vehicle and reliably informs the person of the existence and movement of the vehicle.

However, if the starting forward movement notification sound S is set to a sound (e.g., pseudo engine) similar to the forward moving notification sound D, then the starting forward movement notification sound S will need to be set to a volume larger than the volume of the car horn in order for a driver inside the vehicle cabin to be able to hear the starting forward movement notification sound S and recognize that the forward movement start notification has been issued. However, at such a volume, a person in the surrounding area will be startled by the sound.

Therefore, in this embodiment, the forward movement start sound (S sound) is set to be a soft sound like an electronic ring tone of a software phone that lies in a comparatively low frequency range (as shown in FIG. 7) that readily penetrates the inside of the vehicle cabin from outside the vehicle. Due to its low frequency, such a starting forward movement notification sound S readily penetrates the inside of the vehicle cabin from outside the vehicle such that a driver inside the vehicle cabin can hear the starting forward movement notification sound S and unmistakably recognize that the forward movement start notification has been issued without the forward movement notification sound being set to a large volume (i.e., without startling people in a surrounding area). Also, the starting forward movement notification sound S is not annoying or unpleasant to a driver because it is a soft sound like that of a software phone and it is only emitted for a short period from immediately before the vehicle starts moving forward until the vehicle starts moving forward.

In order to control the starting forward movement notification sound S, the notification sound controller 12 of FIG. 1 executes the control program shown in FIG. 2. In step S11, the notification sound controller 12 checks if the vehicle is in a drivable state. This determination can be accomplished by comparing a current vehicle speed V with a stop determination vehicle speed Vs (e.g., Vs=1 km/h) and/or checking the state of the ignition switch being ON or OFF. If a current vehicle speed V is smaller than the stop determination vehicle speed Vs and the ignition switch is ON, then the notification sound controller 12 determines a drivable state exists. If the vehicle speed V is equal to or larger than the stop determination vehicle speed Vs (e.g., Vs=1 km/h) such that the vehicle is determined to be in a moving state or if the ignition switch is OFF such that the vehicle is in a non-drivable state, then the notification sound controller 12 ends the control sequence and skips step S15 such that the starting forward movement notification sound S is not emitted. Thus, in step S11, the notification sound controller 12 determines that the vehicle is stopped but in a drivable state by checking that the vehicle speed is below a prescribed value and that the state of the ignition switch 18 is ON. In this illustrated embodiment, step S11 of the process executed by the notification sound controller 12 corresponds to a vehicle movement state detecting section.

If the notification sound controller 12 determines that the vehicle is stopped (i.e., V<Vs) and that the vehicle is in a drivable state (ignition switch 18 is ON) in step S11, then the notification sound controller 12 proceeds to step S12. In step S12, the notification sound controller 12 determines if an operation changing the range to the D range (shifted to the drive (D) position) occurred while the brake switch 15 was in an OFF state (i.e., the brake not being operated). If the result of step S12 is Yes, then the notification sound controller 12 proceeds to step S15. In step S15, the notification sound controller 12 drives the cabin exterior speaker 1 such that a soft sound resembling an electronic ring tone of a software phone.

If the result of step S12 is No, then the notification sound controller 12 proceeds to step S13. In step S13, the notification sound controller 12 determines if the brake switch 15 changed from ON to OFF (i.e., if the brake pedal changed from a depressed braking state to a released non-braking state) while the D range was in a selected state. If the result of step S13 is Yes, then the notification sound controller 12 proceeds to step S15. In step S15, the notification sound controller 12 drives the cabin exterior speaker 1 such that a soft S sound resembling an electronic ring tone of a software phone is emitted. In this illustrated embodiment, step S13 of the process executed by the notification sound controller 12 corresponds to a start movement intention detecting section or device.

If the result of step S13 is No, then the notification sound controller 12 proceeds to step S14 and determines if a change to the D range occurred simultaneously or substantially simultaneously with the brake switch 15 being changed from ON to OFF (i.e., if the brake pedal changed from a depressed braking state to a released non-braking state). If the result of step S14 is Yes, then the notification sound controller 12 proceeds to step S15 and drives the cabin exterior speaker 1 such that a soft S sound resembling an electronic ring tone of a software phone is emitted.

In steps S13 and S14, if the brake pedal is being returned slowly from a depressed state and the driver's foot has not yet separated from the brake pedal, then the brake switch 15 will still be ON and not yet changed to OFF. Consequently, the notification sound controller 12 will not proceed to step S15 and the starting forward movement notification sound S cannot be emitted.

If the driver were to mistakenly think that the starting forward movement notification sound S had been emitted while the driver was slowly (gradually) returning the brake pedal, then the driver might start driving while believing that any person in a surrounding area of the vehicle had been warned by the starting forward movement notification sound S that the vehicle would be starting into motion. This would be undesirable from a safety perspective. Furthermore, while the brake pedal is undergoing a slow brake pedal return operation, there is a possibility that the braking force will decline and the vehicle will start moving due to, for example, a creep force or a downward slope of a road surface. Thus, caution is necessary to ensure safety.

However, in this embodiment, as mentioned previously, the starting forward movement notification sound S is a notification sound in a comparatively low frequency range that easily penetrates the inside of the vehicle cabin from outside the vehicle and can be readily heard by the driver. Thus, since the driver can easily recognize when the forward movement start notification has been issued, the driver can also easily recognize that the starting forward movement notification sound S was not emitted during a slow brake pedal return operation. As a result, with this embodiment, the driver will not mistakenly believe that the starting forward movement notification sound S was emitted during a slow brake pedal return operation. In other words, the driver will assume that a person near the vehicle has not heard the starting forward movement notification sound S and is not aware that the vehicle will start moving if the driver has not heard the starting forward movement notification sound S. Thus, the driver can strive to drive safely and a great advantage in terms of driving safety can be achieved.

If the result of step S14 is No, then the notification sound controller 12 ends the control loop and skips step S15 such that the starting forward movement notification sound S is not emitted.

In short, the notification sound controller 12 drives the cabin exterior speaker 1 such that the starting forward movement notification sound S is emitted when any of the following conditions occurs while the vehicle is stopped (V<Vs) and in a drivable state (ignition switch 18 is ON) (step S11): (1) an operation changing the range to the D range occurs while the brake pedal is in a released non-braking state (step S12); (2) the brake pedal changes from a depressed braking state to a released non-braking state while the D range is in a selected state (step S13); or (3) an operation changing the range to the D range occurs simultaneously with the brake pedal changing from a depressed braking state to a released non-braking state (step S14). Otherwise, the cabin exterior speaker 1 remains in a non-driven state and the starting forward movement notification sound S is not emitted.

In this embodiment, the starting forward movement notification sound S is emitted immediately before the vehicle starts moving when the vehicle is stopped in a drivable state (step S11) and a shift operation changing the range to the D range occurs while the brake pedal is in a released (non-braking) state (step S12), a foot depressing the brake pedal releases the brake pedal while the D range is in a selected state (step S13), or a shift operation changing the range to the D range occurs simultaneously with a brake release operation in which a foot depressing the brake pedal is released from the brake pedal (step S14). In other words, in these situations, the starting forward movement notification sound S is emitted immediately by the cabin exterior speaker 1 before the vehicle starts moving (step S15).

If the apparatus were configured to emit the starting forward movement notification sound S when the vehicle enters a drivable state due to the ignition switch 18 being turned ON, then the starting forward movement notification sound S would be emitted too soon and the starting forward movement notification sound S would be emitted unnecessarily during a period from when the vehicle entered the drivable state until immediately before the vehicle starts moving. Consequently, the starting forward movement notification sound S would be emitted for a long time until the vehicle started moving and would bother people (e.g., pedestrians) in an area surrounding the vehicle. Conversely, if the starting forward movement notification sound S is emitted after the vehicle starts moving, then the starting forward movement notification sound S will not serve its purpose of notification that the vehicle will start moving and the meaning of the notification sound will be diminished.

With this embodiment, however, since the starting forward movement notification sound S is emitted immediately before the vehicle starts moving, such a problem as the starting forward movement notification sound S being emitted for a long time before the vehicle starts moving and confusing people (e.g., pedestrians) in a surrounding area or the meaning of the notification provided by the starting forward movement notification sound S being diminished can be avoided.

In order to control the forward moving notification sound D, the notification sound controller 12 of FIG. 1 executes the control program shown in FIG. 3. In step S21, the notification sound controller 12 checks if the starting forward movement notification sound S is being emitted by actuation of the cabin exterior speaker 1. If the starting forward movement notification sound S is being emitted, then the controller 12 proceeds to step S22. In step S22, the notification sound controller 12 checks if a prescribed amount of time has elapsed since the starting forward movement notification sound S started to be emitted (e.g., 500 msec). The controller 12 ends the control loop and continues emitting the starting forward movement notification sound S started in step S15 of FIG. 2 until the prescribed amount of time (500 msec) elapses. Alternatively, instep S22, the prescribed amount of time is a variable amount of time that corresponds to a period from when a driver selects the D range and releases the brake pedal (steps S12 to S14 of FIG. 2), i.e., when the S sound starts being emitted (step S15 of FIG. 2) in response to completion of a movement start preparation operation, until the driver performs a movement start operation. Thus, the prescribed amount of time can be set to any value based on measurement of data or the like, and is not limited to a fixed time period.

When the notification sound controller 12 determines in step S22 that the prescribed amount of time (500 msec) has elapsed since emission of the starting forward movement notification sound S started, i.e., after the starting forward movement notification sound S has been emitted continuously for the prescribed amount of time, the controller 12 proceeds to step S23. In step S23, the notification sound controller 12 executes a cross fade from the starting forward movement notification sound S to the forward moving notification sound D. The cross fade from the starting forward movement notification sound S to the forward moving notification sound D involves gradually lowering a sound pressure level of the starting forward movement notification sound S while gradually increasing a sound pressure level of the forward moving notification sound D (pseudo engine sound) such that the operating state of the cabin exterior speaker 1 gradually changes from the starting forward movement notification sound S to the forward moving notification sound D. As a result, the change from the starting forward movement notification sound S to the forward moving notification sound D can be accomplished without causing a person (e.g., a pedestrian) in a surrounding area to experience an odd feeling about the sounds from the vehicle.

In this embodiment, since the starting forward movement notification sound S is emitted immediately before the vehicle starts moving as described previously with reference to FIG. 2 (steps S12 to S15 in FIG. 2), the starting forward movement notification sound S is emitted at an appropriate timing for notification that the vehicle will start moving. As explained above, the forward moving notification sound D is also emitted at an appropriate timing following the starting forward movement notification sound S. As a result, a situation in which the forward moving notification sound D is emitted long before the vehicle starts moving can be avoided. In this way, the movement notification sound will not cause people (e.g., pedestrians) in a surrounding area to be perplexed and the meaning of the forward movement notification provided by the forward moving notification sound D to be diminished.

If the controller 12 determines in step S21 that the starting forward movement notification sound S is not being emitted from the cabin exterior speaker 1, the controller 12 proceeds to step S24 where the controller 12 checks if the ignition switch 18 is ON, i.e., if the vehicle is in a drivable state. If the controller 12 determines that the vehicle is in a drivable state, then the controller 12 proceeds to step S25. In step S25, the controller 12 checks if the Drive or D range is in a selected state (i.e., if the D range has been selected). If the D range has been selected, then the controller 12 proceeds to step S26. In step S26, the controller 12 determines if the vehicle speed V is equal to or larger than the stop determination vehicle speed Vs, i.e., if the vehicle is moving. If the controller 12 determines that the vehicle is in a drivable state in step S24, that the D range is selected in step S25, and that the vehicle is moving (V≧Vs) in step S26, then the controller 12 proceeds to step S27. In step S27, the controller 12 drives the cabin exterior speaker 1 such that the forward moving notification sound D (pseudo engine sound) is emitted.

The forward moving notification sound D is a pseudo engine sound, as explained previously. The sound volume level of the forward moving notification sound D is held constant. Meanwhile, a frequency of the forward moving notification sound D is set to increase as the vehicle speed increases while remaining within a comparatively high frequency range in which the forward moving notification sound D cannot easily penetrate the cabin interior from outside the cabin. FIG. 9 is a frequency characteristic setting map for the forward moving notification sound D. The frequency of the forward moving notification sound D is set based on a detected vehicle speed. Thus, in this first embodiment, the speed sensor 14 corresponds to a frequency setting device or section. In the first embodiment, the frequency is set to have a linear relationship with respect to the vehicle speed, but it is also acceptable to set the frequency to be an upwardly convex or concave curve in the manner of an exponential function. The sound volume level is not changed but set to a prescribed constant value (corresponds to a sound volume setting section or device); only the frequency is changed. When the forward moving notification sound D is produced in this way as a pseudo engine sound whose sound pressure level stays constant and whose frequency increases as the vehicle speed increases, a person outside the vehicle can judge a distance to the vehicle based on the volume of the forward moving notification sound D. In particular, as the volume of the forward moving notification sound D becomes larger, the person can determine the vehicle is getting closer. Since the volume of the sound emitted from the vehicle is constant, the sound pressure perceived by a person outside the vehicle differs according to distance. Therefore, a person outside the vehicle can judge the distance between him or her and the vehicle based on a difference in sound pressure. Also, the person can judge a speed of the vehicle based on the pitch of the forward moving notification sound D. The higher the pitch of the forward moving notification sound D is, the higher the vehicle speed is. Thus, based solely on the forward moving notification sound D, the person can know approximately how close the vehicle is and how fast it is approaching.

In step S28, the controller 12 determines if the vehicle speed V has reached or exceeded a prescribed vehicle speed (30 km/h), since movement started. This prescribed vehicle speed (30 km/h) corresponds to a minimum prescribed vehicle speed value at which the forward moving notification sound D is no longer necessary. This prescribed vehicle speed (30 km/h) is also called the D sound fade-out speed. Thus, upon the vehicle reaching the D sound fade out speed, the controller 12 starts fading out the forward moving notification sound D. If the result of step S28 is No, then the controller 12 proceeds to step S29 and determines if the vehicle speed V is below a prescribed D sound fade-in speed. In this embodiment, the prescribed D sound fade-in speed is set to 25 km/h, which is lower than the D sound fade-out speed of 30 km/h (minimum vehicle speed value at which the forward moving notification sound D is not necessary) by a hysteresis amount (5 km/h). If the controller 12 determines in step S28 that since vehicle started moving the vehicle speed V has become equal to or larger than the D sound fade-out speed of 30 km/h, then the controller 12 proceeds to step S31. In step S31, the controller 12 drives the cabin exterior speaker 1 such that the forward moving notification sound D emitted in step S27 gradually decreases and disappears (fades out).

If the controller 12 determines in step S29 that the vehicle speed V is below the D sound fade-in speed of 25 km/h, then the controller 12 proceeds to step S32. In step S32, the controller 12 checks if the forward moving notification sound D is being emitted. If the forward moving notification sound D has been stopped due to executing step S31, then the controller 12 proceeds to step S33 where the controller 12 drives the cabin exterior speaker 1 such that the forward moving notification sound D gradually increases from a sound pressure level of 0 (such that the forward moving notification sound D fades in). If the controller 12 determines in step S32 that the forward moving notification sound D is being emitted, then the controller 12 ends the control loop and continues operating the cabin exterior speaker such that the forward moving notification sound D is emitted.

If the controller 12 determines in step S29 that the vehicle speed V is equal to or higher than the D sound fade-in speed (25 km/h), i.e., if controller 12 determines that the vehicle speed V is in a hysteresis region between the D sound fade-out speed 30 km/h and the D sound fade-in speed 25 km/h, then the controller 12 ends the control loop such that the current operating state of the cabin exterior speaker 1 is maintained and the forward moving notification sound D continues to be emitted in the current manner.

If the controller 12 determines in step S24 that the ignition switch 18 is OFF, i.e., that the vehicle is in a non-drivable state, then the forward moving notification sound D is not necessary and the controller 12 proceeds to step S31. In step S31, the controller 12 drives the cabin exterior speaker 1 such that the forward moving notification sound D fades out.

If the controller 12 determines in step S25 that the D range is not selected or if the controller 12 determines that the D range is still in a selected state but determines that the vehicle is stopped in step S26, then the forward moving notification sound D is not necessary and the controller 12 needs to drive the cabin exterior speaker 1 such that the forward moving notification sound D fades out. However, in this case, the forward moving notification sound D control is handled in a special manner that will now be explained. In step S34, the controller 12 determines if the vehicle speed V has been zero (V=0 km/h) continuously for a prescribed amount of time (10 seconds in this embodiment). If the determination result is Yes in step S34, then the controller 12 proceeds to step S31 and drives the cabin exterior speaker 1 such that the forward moving notification sound D fades out. The prescribed amount of time set in step S34 is preferably the amount of time for determining if the vehicle is waiting at a traffic light or traveling on a congested road. It is acceptable to vary the prescribed amount of time by measuring a stop time occurring on a congested road and setting the prescribed amount of time automatically or by allowing a driver to set the prescribed amount of time manually in consideration of a stop time occurring on a congested road. Alternatively, the prescribed amount of time can be variably set based on information provided by a vehicle navigation system or other information provided to the vehicle about the area in which the vehicle is traveling.

If the controller 12 determines in step S34 that the vehicle is not stopped, i.e., that the vehicle speed V is not equal to 0 km/h, or that the vehicle is in a stopped state but the stopped state has not continued for at least the set amount of time (10 seconds), then the controller 12 proceeds to step S35. In step S35, the controller 12 determines if the vehicle is set to park (P), neutral (N), or another non-driving range. In this illustrated embodiment, step S35 corresponds to a driving continuance intent determining section or device. If the determination result is Yes in step S35, then the controller 12 proceeds to step S36. In step S36, the controller 12 determines if the vehicle speed V is smaller than the stop determination vehicle speed Vs, i.e., if the vehicle can be deemed substantially stopped. If the determination result is Yes in step S36, then the controller 12 proceeds to step S31. In step S31, the controller 12 drives the cabin exterior speaker 1 such that the forward moving notification sound D fades out.

In other words, even if the controller 12 has determined in step S34 that the vehicle is not in a stopped state with the vehicle speed V equal to 0 km/h or that the vehicle is in a stopped state but has not been in the stopped state continuously for at least a set amount of time (10 seconds), the controller 12 still executes a fade out of the forward moving notification sound D (step S31) if the selected range is a non-driving range (park or neutral) (step S35) and the vehicle speed V is below the stop determination vehicle speed Vs (step S36).

However, if the selected range is determined not to be a non-driving range (park or neutral) in step S35, or if the selected range is determined to be a non-driving range (park or neutral) in step S35 but the vehicle speed V is determined to be equal to or larger than the stop determination vehicle speed Vs (i.e., the vehicle is determined to be moving) in step S36, then it is necessary to emit the forward moving notification sound D. Thus, the controller 12 proceeds to step S27 where the controller 12 continues to drive the cabin exterior speaker 1 such that the forward moving notification sound D is emitted.

When the range is changed from the D range to a non-driving range (park or neutral), there is a possibility that the vehicle will still move due to inertia. Thus, the apparatus is configured to continue emitting the forward moving notification sound D from the cabin exterior speaker 1 when the selected range is determined to be a non-driving range (park or neutral) in step S35 but the vehicle speed V is determined to be equal to or larger than the stop determination vehicle speed Vs (i.e., the vehicle is determined to be moving) in step S36. In this way, a person who is in a vicinity of a front end portion of the vehicle when the vehicle moves due to inertia in such a case can be urged to exercise caution by the movement notification sound.

In this embodiment, when the controller 12 determines that the D range is not in a selected state in step S25 or when the D range is still in a selected state but the controller 12 determines that the vehicle is stopped in step S26, the controller does not proceed immediately to step S31 and fade the forward moving notification sound D out. Instead, the controller 12 continues emitting the forward moving notification sound D until it executes step S34 and only then proceeds to step S31. In step S31, the controller 12 fades the forward moving notification sound D out if the controller 12 determines that the vehicle speed V has equaled 0 km/h, i.e., that the vehicle has been in a stopped state, for a set amount of time (10 seconds). Thus, when the vehicle is on a congested road or in another situation in which the vehicle stops but the vehicle speed V does not remain at 0 km/h (stopped state) for the set amount of time (10 seconds), an annoying situation can be avoided in which the forward moving notification sound D fades out and then again emitted in accordance with the starting forward movement notification sound S control shown in FIG. 2 (step S15) every time the vehicle stops. In order to achieve this objective even more effectively, it is acceptable to vary the prescribed amount of time by measuring a stop time occurring on a congested road and setting the prescribed amount of time automatically or by allowing a driver to set the set amount of time manually in consideration of a stop time occurring on a congested road.

In this embodiment, the starting forward movement notification sound S is emitted in step S15 of FIG. 2 when the controller 12 is determined in step S13 or step S14 that the brake pedal has been released and the brake switch 15 has changed from ON to OFF. Consequently, when the brake pedal is being released gradually from a depressed state but the brake pedal has not yet been released, the starting forward movement notification sound S is not emitted, i.e., the step S15 is not executed, until the brake switch 15 changes from ON to OFF.

During a slow brake pedal return operation, there is a possibility that the braking force will decline and the vehicle will start moving due to, for example, a creep force or a downward slope of a road surface. Therefore, it is necessary to warn a person in a vicinity of the vehicle if the vehicle starts to move. However, since a notification of a vehicle starting to move in this manner would occur after the vehicle has started to move, the forward moving notification sound D is more appropriate than the starting forward movement notification sound S.

In this embodiment, as shown in FIG. 3, the controller 12 proceeds from step S21 of FIG. 3 to steps S24 to S26 during a situation in which the brake pedal is undergoing a slow return operation such that the starting forward movement notification sound S is not emitted. If the controller 12 determines in step S26 that the vehicle speed V is equal to or larger than the stop determination vehicle speed Vs, i.e., that the vehicle is moving, then the controller proceeds to step S27 and emits the forward moving notification sound D. Consequently, the forward moving notification sound D is emitted instead of the starting forward movement notification sound S when the vehicle starts moving while the brake pedal is undergoing a slow return operation. As a result, when the vehicle starts moving during a slow brake return operation as explained above, a person in a surrounding area can be warned reliably with the more appropriate forward moving notification sound D instead of the starting forward movement notification sound S.

In order to control the reverse movement notification sound R (R sound), the notification sound controller 12 executes the control program shown in FIG. 4. In step S41, the controller 12 checks if the ignition switch 18 is ON, i.e., if the vehicle is in a drivable state. If the vehicle is in a drivable state, then the controller 12 proceeds to step S42. In step S42, the controller 12 checks if vehicle has been placed in reverse (i.e., if the range is set to the R range). If the vehicle is in reverse (R range), then the controller 12 proceeds to step S43. In step S43, the controller 12 drives the cabin exterior speaker 1 such that the reverse movement notification sound R is emitted. Thus, the reverse movement notification sound R is emitted before the vehicle actually starts moving.

Thus, when the ignition switch 18 is ON, i.e., the vehicle is in a drivable state, (step S41) and the vehicle is in reverse, i.e., the R range (step S42), the reverse movement notification sound R is emitted from the cabin exterior speaker 1 immediately (step S43). Since the reverse movement notification sound R is emitted from the cabin exterior speaker 1 immediately when the vehicle is in reverse, i.e., the R range (steps S42 and S43), an “R range selection notification sound” is emitted from the cabin interior speaker 11 simultaneously while the vehicle is in reverse (R range), as explained previously.

As explained previously, since the reverse movement notification sound R emitted from the cabin exterior speaker 1 in step S43 serves to convey the same type of vehicle information as the R range selection notification sound emitted from the cabin interior speaker 11, the reverse movement notification sound R emitted from the cabin exterior speaker 1, too, is configured to be an intermittent sound. The reverse movement notification sound R (intermittent sound) is controlled to be synchronized with the intermittent R range selection notification sound emitted from the cabin interior speaker 11. Thus, in this embodiment, step S43 constitutes cabin interior-exterior notification sound synchronizing section.

It is also acceptable if, conversely, the intermittent R range selection notification sound emitted from the cabin interior speaker 11 is synchronized with the reverse movement notification sound R (intermittent sound) emitted from the cabin exterior speaker 1.

Either way, the reverse movement notification sound R (intermittent sound) emitted from the cabin exterior speaker 1 and the R range selection notification sound emitted simultaneously from the cabin interior speaker 11 are synchronized and the R sound from the cabin exterior speaker 1 (which the driver does not need to hear) is overlaid with the intermittent R range selection notification sound from the cabin interior speaker 11 such that the driver cannot hear it. Thus, the problem of the driver hearing and being annoyed by the unnecessary R sound emitted from the cabin exterior speaker 1 can be alleviated.

Additionally, since the reverse movement notification sound R (intermittent sound) is synchronized with the intermittent R range selection notification sound, the intermittent periods when neither the reverse movement notification sound R (intermittent sound) from the cabin exterior speaker 1 nor the intermittent R range selection notification sound from the cabin interior speaker 11 can be heard, i.e., the periods when the driver can easily hear another notification sound, are longer. Thus, during these longer quiet periods, such other notification sounds as the obstacle proximity notification sound and the seatbelt notification sound mentioned previously can be heard by a driver. In this way, the driver can recognize the notification sounds immediately and obtain the corresponding information reliably, which is greatly advantageous from a safety standpoint.

If the controller 12 determines in step S41 that the ignition switch 18 is OFF, i.e., that the vehicle is in a non-drivable state, then the vehicle cannot move in reverse and it is not necessary to emit the R sound. Therefore, the controller 12 ends the control loop directly and skips step S43 such that the R sound is not emitted (i.e., the cabin exterior speaker 1 is put into a non-driven state).

If the controller 12 determines in step S42 that the R range is not selected, then the controller 12 proceeds to step S44 and determines if a non-driving range (park or neutral) is selected. If the controller 12 determines that the vehicle is not set to a non-driving range (park or neutral), i.e., that the D range is selected, then it is not necessary to emit the reverse movement notification sound R and the controller 12 ends the control loop directly, thereby skipping step S43 such that the reverse movement notification sound R is not emitted (i.e., the cabin exterior speaker 1 is put into a non-driven state).

If the controller 12 determines in step S44 that the vehicle is set to a non-driving range (park or neutral), then the controller 12 proceeds to step S45 and checks if the vehicle speed V is smaller than the stop determination vehicle speed Vs, i.e., if the vehicle can be deemed substantially stopped. If the controller 12 determines that the vehicle is substantially stopped, then the controller 12 proceeds to step S46. In step S46, the controller 12 drives the cabin exterior speaker 1 such that the reverse movement notification sound R emitted in step S43 gradually decreases until it disappears (fades out).

However, if the controller 12 determines that the vehicle is in a non-driving range (park or neutral) in step S44 but that the vehicle speed V is not smaller than the stop determination vehicle speed Vs (i.e., the vehicle is not substantially stopped but determined to be moving), then the controller 12 determines that the vehicle is moving in reverse even though it is in a non-driving range (park or neutral) and proceeds to step S47. In step S47, the controller 12 continues driving the cabin exterior speaker 1 such that the reverse movement notification sound R is started emitting in step S43 continues to be emitted. In this way, in a situation in which the vehicle continues moving in reverse due to inertia after the range is changed from the R range to a non-driving range (park or neutral), the reverse movement notification sound R can continue to be emitted from cabin exterior speaker 1. In this way, a person near a rear end portion of the vehicle can be reliably warned that the vehicle is moving backward and be urged to exercise caution.

A situation in which the reverse movement notification sound R is emitted in step S47 can only occur if the controller 12 has determined in step S42 that the R range is not in a selected state. In such a situation, as should be clear from the previous explanation, the R range selection notification sound is not emitted from the cabin interior speaker 11 and, thus, it is not necessary to synchronize an R range selection notification sound emitted from the cabin interior speaker 11 with the R sound from the cabin exterior speaker 1 as is done in step S43.

As explained previously with reference to FIGS. 2 and 3, the forward moving notification sound D is emitted when a prescribed amount of time, e.g., 500 msec, has elapsed (step S22 of FIG. 3) since the starting forward movement notification sound S started being emitted (step S15 of FIG. 2) in response to the D range being selected by a driver from a stopped state (step S11 of FIG. 2) and an operation being performed by the driver in preparation to start the vehicle into motion, e.g., releasing the brake pedal, (steps S12 to S14 of FIG. 2). Conversely, as explained previously with reference to FIG. 4, the reverse movement notification sound R is emitted immediately (step S43 of FIG. 4) when the driver selects the R range (step S42 of FIG. 4). The reason the reverse movement notification sound R is emitted immediately will now be explained.

A vehicle is intended chiefly for driving forward and driving in reverse is more difficult for a driver than driving forward. Moreover, a person (e.g., a pedestrian) in a surrounding area of a vehicle tends to assume that a vehicle typically moves in a forward direction and naturally exercises caution with respect to forward movement of a vehicle. Conversely, a person does not expect a vehicle to move in reverse and tends to exercise less caution in anticipation of reverse movement.

In short, the reverse movement notification sound R is intended as a notification of reverse movement indicating movement in a direction a driver is less accustomed to and a direction a person (e.g., a pedestrian) in a surrounding area is less likely to expect. Therefore, from a safety standpoint, it is preferable for the reverse movement notification sound R to be emitted as early as possible to urge people in a surrounding area to exercise caution. Conversely, the forward moving notification sound D is intended as a notification of forward movement indicating movement in a direction a driver is more accustomed to and a direction a person (e.g., a pedestrian) in a surrounding area is more likely to expect as a natural direction for a vehicle to move. Moreover, as explained previously, the forward moving notification sound D is a pseudo engine sound and it is better to keep an emission time of the forward moving notification sound D as short as possible in order to ensure the quietness of the vehicle. Therefore, it is preferable for the forward moving notification sound D to be emitted as late as possible.

Thus, as mentioned above, each notification sound (the S sound, the D sound and the R sound) is emitted under different respective vehicle conditions in this embodiment. In particular, in this embodiment, the apparatus is configured such that the reverse movement notification sound R is emitted immediately (step S43 of FIG. 4) when a driver performs an operation selecting the R range (step S42 of FIG. 4). Also, in this embodiment, the apparatus is configured such that the forward moving notification sound D is emitted after a prescribed amount of time, e.g., 500 msec, has elapsed (step S22 of FIG. 3) since the software phone-like sound of the starting forward movement notification sound S was started being emitted (step S15 of FIG. 2) in response to the D range being selected by a driver from a stopped state (step S11 of FIG. 2) and an operation being performed by the driver in preparation to start the vehicle into motion, e.g., releasing the brake pedal, (steps S12 to S14 of FIG. 2). By configuring the apparatus in this way, the notification sounds emitted for forward movement and reverse movement can each be emitted at a necessary timing and for a necessary period of time without confusing a person (e.g., a pedestrian) in a surrounding area by emitting unnecessary notification sounds. In this embodiment, steps S12 to S15 of FIG. 2 constitute a notification sound emission timing section. In this embodiment, step S43 of FIG. 2 constitutes a reverse notification sound emission timing section.

There are situations in which a notification sound (e.g., the S sound, the D sound, and the R sound) emitted from the cabin exterior speaker 1 like the starting forward movement notification sound S, the forward moving notification sound D, or the reverse movement notification sound R could be an annoying disturbance to others, such as late at night or in a residential neighborhood. In such a situation, a driver can issue a notification sound prohibition command by pressing the mute switch 16 shown in FIG. 1. The mute switch 16 is configured to issue a notification sound prohibition command each time it is pressed such that it enters an ON state. When it is not being pressed, it automatically resumes a normal position (OFF position).

When the controller 12 receives the notification sound prohibition command from the mute switch 16, the controller 12 shown in FIG. 1 executes a control program shown in FIG. 5 and prohibits emission of notification sounds (the S sound, the D sound and the R sound) as will now be explained.

In step S51, the controller 12 checks if the mute switch 16 has been turned ON, i.e., if the notification sound prohibition command has been issued. If the mute switch 16 is not ON (if the notification sound prohibition command has not been issued), then the controller 12 ends the control loop and does not execute a prohibition of the notification sounds. As a result, the notification sounds are emitted as explained previously with reference to FIGS. 2 to 4.

If the controller 12 determines in step S51 that the mute switch 16 has been turned ON (that the notification sound prohibition command has been issued), then the controller 12 proceeds to step S52. In step S52, the controller 12 prohibits the emission of notification sounds such that the notification sounds (the S sound, the D sound and the R sound) are not emitted from the cabin exterior speaker 1 regardless of the state of the controls shown in FIGS. 2 to 4.

Next, in step S53, the controller 12 determines if the vehicle speed V is equal to or larger than the 30 km/h, which is a minimum vehicle speed value at which the forward moving notification sound D is not necessary (D sound fade-out vehicle speed) as explained previously regarding step S28 of FIG. 3. If the result of this determination is No in step S53, then the controller 12 ends the control loop and continues the notification sound emission prohibition started in step S52. If the controller 12 determines in step S53 that the vehicle speed V is equal to or larger than the D sound fade-out speed (30 km/h), then the controller 12 proceeds to step S54. In step S54, the controller 12 cancels the notification sound emission prohibition started in step S52, thereby allowing the notification sounds (the S sound, the D sound and the R sound) to be emitted from the cabin exterior speaker 1 in accordance with the controls shown in FIGS. 2 to 4.

With the notification sound prohibition control just described, a driver can prohibit the emission of notification sounds (the S sound, the D sound and the R sound) from the cabin exterior speaker 1 (step S52) regardless of the state of the controls shown in FIGS. 2 to 4 by pressing the mute switch 16 (step S51). Thus, emission of the notification sounds can be prevented in situations where a notification sound emitted from the cabin exterior speaker 1, i.e., the starting forward movement notification sound S, the forward moving notification sound D, or the reverse movement notification sound R, could be an annoying disturbance to other people (e.g., pedestrians) in a surrounding area, such as late at night or in a residential neighborhood.

However, if the emission of notification sounds continues to be prohibited after the driver presses the mute switch 16, then the notification sounds will not be emitted even after the vehicle has traveled to an area where the notification sounds will not be a disturbance and the apparatus will not serve its purpose as a safety device. Therefore, in this embodiment, if the vehicle speed V reaches or exceeds the D sound fade-out speed (30 km/h) (step S53), then the controller 12 determines that the vehicle has traveled to a place where the notification sounds will not disturb anyone and cancels the notification sound emission prohibition (step S54). In this way, the notification sounds (the S sound, the D sound and the R sound) can be emitted from the cabin exterior speaker 1 in accordance with the controls shown in FIGS. 2 to 4.

By canceling the prohibition in this way, a situation in which the notification sounds are not emitted even after the vehicle has traveled to a place where the notification sounds will not disturb anyone be avoided and the notification apparatus can serve its purpose as a safety apparatus.

In this embodiment, the vehicle speed V reaching or exceeding the D sound fade-out speed (30 km/h) is used as a condition for canceling the notification sound prohibition. Certain operational effects can be obtained by contriving the apparatus to determine that the vehicle has traveled to a place where the notification sounds will not disturb anyone and cancel the notification sound prohibition when that condition is satisfied. Those effects will now be explained.

If the condition for canceling the notification sound prohibition is set to a vehicle speed V that is slower than the forward moving notification sound D fade out vehicle speed (30 km/h), then it will be possible for the prohibition to be canceled while the vehicle is still in a place where the notification sounds could disturb other people in a surrounding area. More specifically, as explained previously, the region of low vehicle speeds below 30 km/h is the region in which the apparatus is configured to emit the forward moving notification sound D. Meanwhile, it is in this same low vehicle speed region that a driver might press the mute switch 16 (turns it ON) to prohibit the notification sounds from being a disturbance. If the cancellation condition is a vehicle speed in this low vehicle speed region, then the notification sound prohibition might be cancelled immediately after a driver releases his or her finger from the mute switch 16, thus allowing a notification sound to disturb a person (e.g., a pedestrian) in a surrounding area of the vehicle.

In this embodiment, however, the condition for cancelling the notification sound prohibition is that the vehicle speed V is equal to or larger than the D sound fade-out speed (30 km/h) and the notification sound prohibition is cancelled when this condition is satisfied. Consequently, when a driver turns the mute switch 160N while the vehicle speed V is below the D sound fade-out speed (30 km/h) (i.e., while the vehicle speed is in a low vehicle speed region where the forward moving notification sound D is emitted), the prohibition of the notification sounds is not cancelled when the driver's finger leaves the mute switch 16. Instead, the prohibition continues and the problem of a notification sound being emitted while the vehicle is traveling in a place where the notification sound can be a disturbance to a person (e.g., a pedestrian) in a surrounding area can be avoided.

When the vehicle is traveling at or in an area surrounding a manufacturing plant, a busy shopping area, or other noisy place (e.g., a place where a noise level is high), it may be difficult for a person (e.g., a pedestrian) in a surrounding area to hear the starting forward movement notification sound S, the forward moving notification sound D, the reverse movement notification sound R or other notification sound emitted from the cabin exterior speaker 1 and difficult for the purpose of the notification to be accomplished if the notification sound is emitted at a standard sound pressure level. In such a situation, a driver can issue a notification sound volume increase command by pressing a sound volume increasing switch 17 shown in FIG. 1. The sound volume increasing switch 17 is configured to issue a notification sound volume increase command each time it is pressed such that it enters an ON state. When it is not being pressed, it automatically resumes a normal position (OFF position).

As explained previously, the forward moving notification sound D is a notification sound set to such a frequency that it is readily audible to a person in an outside area surrounding the vehicle. Thus, the forward moving notification sound D can generally be heard even in a busy shopping area or other noisy place and it is not mandatory to provide the ability to increase the volume of the forward moving notification sound D. However, this embodiment is configured to enable the volume of the forward moving notification sound D to be increased in anticipation of particularly harsh environments in which the forward moving notification sound D is difficult to hear in spite of its highly audible frequency.

When the controller 12 receives the notification sound volume increase command from the sound volume increasing switch 17, the notification sound controller 12 shown in FIG. 1 executes a control program shown in FIG. 6 and increases the volume of the notification sounds as will now be explained. In step S61, the controller 12 checks if the sound volume increasing switch 17 has been turned ON, i.e., if the notification sound volume increase command has been issued. If the sound volume increasing switch 17 is not ON (if the notification sound volume increase command has not been issued), then the controller 12 ends the control loop and does not execute a volume increase of the notification sounds. As a result, the notification sounds are emitted as explained previously with reference to FIGS. 2 to 4 and the sound pressure level of the notification sounds remains at a standard value.

If the controller 12 determines in step S61 that the sound volume increasing switch 17 is ON (i.e., that the notification sound volume increase command has been issued), then the controller 12 proceeds to step S62 and increases the volume of the notification sounds such that a notification sound (S sound, D sound, or R sound) emitted from the cabin exterior speaker 1 in accordance with the controls explained in FIGS. 2 to 4 is emitted at a higher sound pressure level than the standard value.

In step S63, the controller 12 determines if a prescribed amount of time (e.g., one minute) has elapse since the sound volume increasing switch 17 was turned ON (i.e., since the notification sound volume increase command was issued). If the determination result is No, i.e., if the prescribed amount of time still has not elapsed since the sound volume increasing switch 17 was turned ON (i.e., since the notification sound volume increase command was issued), then the controller 12 ends the control loop and continues executing the notification sound volume increase started in step S62. When the controller 12 determines in step S63 that the prescribed amount of time has elapsed since the sound volume increasing switch 17 was turned ON (i.e., since the notification sound volume increase command was issued), the controller 12 proceeds to step S64 and cancels the notification sound volume increase executed in step S62, thereby lowering the sound pressure level of the notification sounds (the S sound, the D sound and the R sound) emitted from the cabin exterior speaker 1 in accordance with the controls shown in FIGS. 2 to 4 back to the standard value.

With the notification sound volume increase control described above, when the vehicle is traveling at or in an area surrounding a manufacturing plant, a busy shopping area, or other noisy place where it may be difficult for a person in a surrounding area to hear a notification sound emitted from the cabin exterior speaker 1, a driver can increase a volume of the notification sounds by pressing the sound volume increase switch 17 (step S61) such that the controller increases a sound pressure level (step S62) of the notification sounds (the S sound, the D sound and the R sound) emitted from the cabin exterior speaker 1 in accordance with the controls shown in FIGS. 2 to 4. In this way, a person in a surrounding area is enabled to hear a notification sound emitted from the cabin exterior speaker 1 even at or in an area surrounding a manufacturing plant, a busy shopping area, or other noisy place.

If the increased volume state of the notification sounds were to continue after the sound volume increasing switch 17 is pressed by a driver, then the notification sounds would be too loud when the vehicle traveled to a residential area or other less noisy place (i.e., a place with a low noise level) and become a disturbance to people in a surrounding area. In particular, in this embodiment, the forward moving notification sound D is a pseudo engine sound in a comparatively high frequency range that does not readily enter the cabin interior from outside the cabin. Since the forward moving notification sound D is difficult for a driver inside the cabin to hear, it is easy for the driver to forget to return (lower) the volume level. Therefore, this embodiment is configured to cancel the volume increase of the notification sounds (step S64) when a prescribed amount of time has elapsed (step S63) since the sound volume increasing switch 17 was turned on (i.e., since the notification sound volume increase command was issued), thereby lowering the sound pressure level of the notification sounds (the S sound, the D sound and the R sound) emitted from the cabin exterior speaker 1 in accordance with the controls shown in FIGS. 2 to 4 back to a standard level.

Thus, it is assumed that by the time the prescribed amount of time has elapsed since the sound volume increasing switch 17 was turned ON, the vehicle will have traveled to a less busy suburban area, residential area, or other quieter place. By lowering the notification sounds (the S sound, the D sound and the R sound) emitted from the cabin exterior speaker 1 back to the standard sound pressure level, the increased volume of the notification sounds resulting when the sound volume increasing switch 17 is turned ON can be prevented from disturbing people in a near the vehicle when the vehicle is in a quieter place.

The operational effects of a notification sound emitting apparatus according to this embodiment will now be explained.

If the vehicle is an engine-driven vehicle that uses only an engine as a power source, then when the vehicle is stopped but in a drivable state (i.e., in a state in which the starting forward movement notification sound S would be emitted), a pedestrian near the vehicle can recognize that the vehicle could possibly start into motion based on the idling sound of the engine. However, if the vehicle is an electric car or in a traveling mode in which only an electric motor is used as a power source, then an operating sound of the vehicle is quiet and it is difficult for a pedestrian to recognize that the vehicle could possibly start moving from a stopped state. Therefore, when the vehicle is stopped, it is necessary to inform pedestrians that the vehicle might start moving.

Therefore, in the illustrated embodiment, the vehicle notification sound emitting apparatus is configured such that a frequency of a forward moving notification sound D emitted to an outside of the vehicle is set to a frequency in the range 1.5 kHz to 6 kHz, which corresponds to a frequencies in a vicinity where the equal loudness level curves shown in FIG. 8 indicate a minimum sound pressure level and a frequencies in a vicinity where a sound insulating property of a cabin interior can effectively suppress penetration of the movement notification to a permissible level. As a result, a person in an outside area surrounding the vehicle can hear the forward moving notification sound D but the forward moving notification sound D does not easily penetrate the cabin interior from outside the vehicle.

Thus, with this embodiment, a person in an outside area surrounding the vehicle can hear the forward moving notification sound D in a reliable fashion without using a sound volume increasing means or other special measure like that mentioned in Japanese Laid-Open Patent Publication No. 2002-233001, and a situation in which an unnecessary forward moving notification sound D penetrates into the cabin interior and becomes unpleasant for a driver and/or passenger can be prevented. In short, all of the previously described problems are solved.

An upper limit frequency of the forward moving notification sound D is set to 6 kHz, which corresponds to a limit frequency beyond which it is difficult for an older person to hear. As a result, an older person whose hearing sensitivity has declined can readily hear the forward moving notification sound D, which is advantageous from a safety standpoint.

Within the frequency range of 1.5 kHz to 6 kHz, the frequency range of 2 kHz to 4 kHz (indicated as an optimum audible frequency range in FIG. 8) is a range in which a sensitivity of the human ear is highest due to resonance of the external ear canal. Thus, by setting the frequency of the forward moving notification sound D to a frequency in the latter range, the previously explained operational effects (i.e., the effect of enabling a person in an area surrounding the vehicle to hear the forward moving notification sound D in a reliable manner and the effect of preventing the forward notification sound (D sound) from unnecessarily penetrating the cabin interior and becoming unpleasant for a driver and/or passenger) can be obtained in an even more marked manner.

In the illustrated embodiment, a volume of a notification sound is held constant while its frequency is varied according to a vehicle speed. In other words, the notification sound emitting apparatus includes a sound volume setting section and a frequency setting section. The sound volume setting section is configured to set a volume of the notification sound to a prescribed value. The frequency setting section is configured to set a frequency of the notification sound such that the higher a vehicle speed becomes, the higher the frequency becomes. Since the volume of the sound is fixed, a person in a surrounding area of the vehicle can sense a sound pressure that varies according to distance. That is, since the volume of the sound source is constant, a sound pressure that reaches the ears of a pedestrian attenuates in accordance with the distance between the pedestrian and the sound source. Consequently, the sound pressure is smaller when the distance is far and larger when the distance is near. In other words, information regarding a distance between a vehicle and a person in a surrounding area of the vehicle can be conveyed from the vehicle to the person. Additionally, since the frequency of the sound changes in accordance with the vehicle speed, a pedestrian in a surrounding area of the vehicle can sense a pitch difference of the sound that varies according to vehicle speed. In other words, information regarding the vehicle speed can be conveyed from the vehicle to the person. Therefore, a person in an area surrounding the vehicle can gain an idea of the distance between him or her and the vehicle and the speed of the vehicle based on the sound pressure and pitch of the sound that the person senses.

In the illustrated embodiment, the controller 12 is provided with a driver start movement intention detecting section and a vehicle movement state detecting section. The start movement intention detecting section is configured to detect if a driver intends to start a vehicle into motion. The vehicle movement state detecting section is configured to detect if the vehicle is moving or not. When the driver start movement intention detecting section detects an intent to start the vehicle into motion and the vehicle movement state detecting section has not detected that the vehicle is moving, the controller 12 emits a forward movement notification sound having a prescribed frequency that easily penetrates a cabin interior from outside the cabin. Meanwhile, when the vehicle movement state detecting section has detected that the vehicle is moving, the controller 12 emits a movement notification sound having a frequency that is higher than said prescribed frequency. Due to its low frequency, the starting forward movement notification sound S readily penetrates the inside of the vehicle cabin from outside the vehicle such that a driver inside the vehicle cabin can hear the starting forward movement notification sound S and unmistakably recognize that the forward movement start notification has been issued without the forward movement notification sound being set to a large volume (i.e., without startling people in a surrounding area). Meanwhile, the forward moving notification sound D is set to a comparatively high frequency that does not readily penetrate a cabin interior from a cabin exterior such that the forward moving notification sound D is not heard unnecessarily by a driver inside the cabin. As a result, the forward movement notification sound does not become an unpleasant annoyance for the driver.

The start movement intention detecting section is configured to detect if the vehicle is in a drivable state and the vehicle speed is smaller than a prescribed vehicle speed indicating that the vehicle is stopped, and the movement state detecting means is configured to detect if the vehicle speed is equal to or larger than the prescribed vehicle speed. It is meaningless to emit the forward movement notification sound while the vehicle is already moving, and the forward movement notification sound becomes an unpleasant annoyance to a driver if it is emitted continuously while the vehicle is stopped. Meanwhile, it is possible to detect a short period of time from immediately before the vehicle is started into motion until the vehicle starts moving by determining that the vehicle is about to start into motion when the vehicle is both stopped and in a drivable state. As a result, the starting forward movement notification sound S can be emitted for an appropriately short period of time at an appropriate timing.

In the illustrated embodiment, the starting forward movement notification sound S is emitted when the results of step S12, step S13, and step S14 are all Yes, i.e., when the driver has completed a D range selecting operation and a brake disengaging operation (such that the brake switch 15 turns OFF). Normally, when a driver is going to start driving a vehicle forward, the driver changes the selected range from the P range to the D range while depressing the brake pedal and then the driver moves his or her foot from the brake pedal to the accelerator pedal and depresses the accelerator pedal. Thus, by detecting if both the D range selecting operation and the brake disengaging operation have been completed, the apparatus can detect if the driver has completed operations in preparation for driving forward and is waiting to depress the accelerator, i.e., if the vehicle is in a state corresponding to a time immediately before the vehicle starts moving. By emitting the starting forward movement notification sound S when the D range selecting operation and the brake disengaging operation have been completed, pedestrians in a surrounding area of the vehicle can be informed that the vehicle will start moving forward from a stop.

With the control program for the starting forward movement notification sound S shown in FIG. 2, during a period when a driver is gradually returning the brake pedal from a depressed state toward a released state but has not yet released the brake pedal, the controller 12 skips step S15 and does not emit the starting forward movement notification sound S because the brake switch 15 has not yet changed from ON to OFF. During a brake pedal return operation like that described above, there is a possibility that the braking force will decline and the vehicle will start moving due to, for example, a creep force or a downward slope of a road surface. In this kind of situation, too, it is necessary to warn pedestrians in a vicinity of the vehicle. However, since a notification of a vehicle starting to move in this manner would occur after the vehicle has started to move, the forward moving notification sound D (which serves to warn of movement in progress) is more appropriate than the starting forward movement notification sound S (which indicates a state immediately before movement starts). Additionally, since the vehicle is moving slowly with a brake force applied, emitting the starting forward movement notification sound S could possibly give pedestrians in the surrounding area a false impression that the vehicle will start moving rapidly (while accelerating).

Therefore, in this embodiment, as shown in FIG. 3, when the vehicle starts moving forward due to a slow brake return operation during which the starting forward movement notification sound S is not emitted, the controller 12 proceeds from step S21 of FIG. 3 to steps S24 through S26. Then, when the vehicle speed V is determined to be equal to or larger than the stop determination vehicle speed Vs in step S26, the controller 12 proceeds to step S27 and emits the forward moving notification sound D.

Thus, when a driver performs a gradual return operation of the brake pedal while the vehicle is in a stopped state and the vehicle starts moving due to a diminished braking force, the starting forward movement notification sound S is canceled and the forward moving notification sound D is emitted immediately so that a pedestrian in the surrounding area can be warned of the vehicle movement by the forward moving notification sound D (which is intended to warn of movement in progress) instead of the less appropriate S sound (which is intended to warn of impending movement). Also, since the starting forward movement notification sound S, which is normally emitted immediately before movement starts, is not emitted, pedestrians in a surrounding area can recognize that the vehicle is moving slowly.

In this embodiment, as mentioned previously, the starting forward movement notification sound S is a notification sound in a prescribed region of comparatively low frequencies that easily penetrate the inside of the vehicle cabin from outside the vehicle cabin and can be readily heard by the driver. Thus, since the driver can easily recognize when the forward movement start notification has been issued, the driver can also easily recognize that the starting forward movement notification sound S was not emitted during a slow brake pedal return operation. As a result, with this embodiment, the driver will not mistakenly think that the starting forward movement notification sound S was emitted during a slow brake pedal return operation and the driver will assume that a person near the vehicle has not heard the starting forward movement notification sound S and is not aware that the vehicle will start moving. Thus, the driver can strive to drive safely and a great advantage in terms of driving safety can be achieved.

While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, although the previously explained embodiment presents the idea of setting a frequency of the forward moving notification sound D in a special manner, as already explained, the reverse movement notification sound (R), too, is a movement notification sound and it is acceptable to set a frequency of the reverse movement notification sound R in a similar manner as the forward moving notification sound D to obtain a similar effect. Also it is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the vehicle notification sound emitting apparatus are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. 

1. A vehicle notification sound emitting apparatus comprising: a sound emitting device configured to emit a movement notification sound to outside of a vehicle to inform a person in an outside area surrounding the vehicle that the vehicle will move or is moving; and a notification sound control device configured to operate the sound emitting device in response to occurrence of a vehicle condition, the notification sound control device setting the movement notification sound of the sound emitting device to a frequency in a range of 1.5 kHz to 6 kHz such that the movement notification sound is audible by the person in the outside area surrounding the vehicle, but inaudible to a vehicle occupant in a closed cabin interior of the vehicle, the notification sound control device holding a sound volume of the movement notification sound emitted to a constant level while the frequency of the movement notification sound is increased as a vehicle speed increases.
 2. The vehicle notification sound emitting apparatus as recited in claim 1, wherein the notification sound control device sets the movement notification sound of the sound emitting device to a frequency in a range of 2 kHz to 4 kHz.
 3. (canceled)
 4. The vehicle notification sound emitting apparatus as recited in claim 1, wherein the notification sound control device includes a driver start movement intention detecting section that detects a driver's intention to start the vehicle into motion, and a vehicle movement state detecting section that detects vehicle movement, the sound emitting device emits a starting forward movement notification sound having a prescribed frequency that penetrates a cabin interior from a cabin exterior such that the starting forward movement notification sound is inaudible to the vehicle occupant in response to the vehicle start movement intention detecting section detecting the driver's intention to start the vehicle into motion and the vehicle movement state detecting section not detecting that the vehicle is moving, and the sound emitting device emits the movement notification sound with a frequency that is higher than the prescribed frequency of the starting forward movement notification sound in response to the vehicle movement state detecting section detecting that the vehicle is moving.
 5. The vehicle notification sound emitting apparatus as recited in claim 4, wherein the start movement intention detecting section detects the driver's intention to start the vehicle into motion based on a drivable state of the vehicle existing and the vehicle speed being smaller than a prescribed vehicle speed indicating that the vehicle is stopped; and the vehicle movement state detecting section detects vehicle movement based on the vehicle speed being equal to or larger than the prescribed vehicle speed.
 6. The vehicle notification sound emitting apparatus as recited in claim 1, wherein the notification sound control device controls the sound emitting device to produce the movement notification sound as a forward movement notification sound upon determining the vehicle condition is in a state indicative of a forward advancement state of the vehicle and as a reverse movement notification sound upon determining the vehicle condition is in a state indicative of a reverse advancement state of the vehicle, the forward movement notification sound being different from the reverse movement notification sound.
 7. A vehicle notification sound emitting apparatus comprising: a sound emitting device configured to emit a movement notification sound to an outside of a vehicle to which the vehicle notification sound emitting apparatus is mounted to inform a person in a surrounding area that the vehicle will move or is moving; and a notification sound control device configured to operate the sound emitting device in response to occurrence of a vehicle condition, the notification sound control device setting the movement notification sound of the sound emitting device to a frequency in a selected frequency range where equal loudness level curves correspond to a minimum sound pressure level and the movement notification sound is audible by the person in an outside area surrounding the vehicle, but inaudible to a vehicle occupant in a closed cabin interior in that frequencies in the selected frequency range do not easily penetrate the cabin interior from outside the vehicle due to sound insulating property of the cabin interior, the notification sound control device holding a sound volume of the movement notification sound emitted to a constant level while the frequency of the movement notification sound is increased as a vehicle speed increases.
 8. The vehicle notification sound emitting apparatus as recited in claim 7, wherein the notification sound control device sets the movement notification sound of the sound emitting device to a frequency in a range of 2 kHz to 4 kHz.
 9. The vehicle notification sound emitting apparatus as recited in claim 7, wherein the notification sound control device includes a driver start movement intention detecting section that detects a driver's intention to start the vehicle into motion, and a vehicle movement state detecting section that detects vehicle movement, the sound emitting device emits a starting forward movement notification sound having a prescribed frequency that penetrates a cabin interior from a cabin exterior such that the starting forward movement notification sound is inaudible to the vehicle occupant in response to the vehicle start movement intention detecting section detecting the driver's intention to start the vehicle into motion and the vehicle movement state detecting section not detecting that the vehicle is moving, and the sound emitting device emits the movement notification sound with a frequency that is higher than the prescribed frequency of the starting forward movement notification sound in response to the vehicle movement state detecting section detecting that the vehicle is moving.
 10. The vehicle notification sound emitting apparatus as recited in claim 9, wherein the start movement intention detecting section detects the driver's intention to start the vehicle into motion based on a drivable state of the vehicle existing and the vehicle speed being smaller than a prescribed vehicle speed indicating that the vehicle is stopped; and the vehicle movement state detecting section detects vehicle movement based on the vehicle speed being equal to or larger than the prescribed vehicle speed.
 11. The vehicle notification sound emitting apparatus as recited in claim 7, wherein the notification sound control device controls the sound emitting device to produce the movement notification sound as a forward movement notification sound upon determining the vehicle condition is in a state indicative of a forward advancement state of the vehicle and as a reverse movement notification sound upon determining the vehicle condition is in a state indicative of a reverse advancement state of the vehicle, the forward movement notification sound being different from the reverse movement notification sound. 